Differential froth flotation process



OL/54b w AEAD CONCENTEATE D Dec. 29, 1953 P. R. HINES DIFFERENTIAL FROTH FLOTATION PROCESS Filed Dec. 26, 1950 3 Sheeis-Sheet 1 x {00 0.5, 1 2 3 4 Q \q g 95 o .90 Q i. g 85 IN VEN TOR. Pierre /2. Hines ATTOR/YEY OF TOTAL Z/NC /N LEAD CONCENTIQATE Dec.. 29, 1953 P. R. HINES DIFFERENTIAL FROTH FLOTATION PROCESS Filed Dec. 26, 1950 70 RECOVERY LEAD 7LEAD //V LEAD CO/YCENTPATE 3 Sheets-Sheet 2 L5.PER TON 0F UREA, 2L8. Na, c0, PEI? TON it Q N E z l 55 E 6 x INVENTOR.

Pie/he R. Hines BY v ATTORNEY I Dec. 29, 1953 P. R. HINES 2,664,198

DIFFERENTIAL FROTH FLOTATION PROCESS Filed Dec. 26, 1950 3 Sheets-Sheet 3 L6. PER TON OF 0054 31.5. N0 co, P52 TON Q 0 0.05 0./ 0.2 0.3 0.4 E 95 E E5 2 8 8 90 t 8 Q E v 2 lg 55 Q l E E a g 51: 5 E 55 Q U m 50 E \l E 3 111 .5 E

IN VEN TOR. Pierre 2. Hines ATTORNEY Patented Dec. 29, 195?;

umrsc EBENTIAL F H FLQTATIQN PROCESS ..p c ABBHQQQ"?! QQPG P F 26, .59; 5 2 i 91 972 643 4 claims (01. 2099167),

Thisinv ention relates, broadly, to the-sepia.-v ration of minerals andthe concentration of ores by froth flotation; more particularly, it relates to the separation of lead and zinc irom an ore containing these.

hisin ti n ba ed P1 9 he d s veiy ha urea and its derivatives are effective flotation nts and 9. 1 3 1 c d e t s c yas il?- efal collecting agents in froth flotation operatons.-

n a ircui c c atroll sfa lih tyand g e mp c ed esu th d fiere fia fl ai o b omlc ce -z c o s T e can twe "seven tage in flotation operations on -lead-zincores uridei" controlled conditions of alkalinity because they do not require the'v arious supplementary reagents such as conditioners and d'epressersoi,

if these are required, asmaller quantity can be T e comp un w h can be employed are represented by the formula:

'l'hese compounds, R1, R2, R3, and R4, alfe'hy drogen' a l ph o na cmstic 8, 9 11. 5 I

particularly, one can employ as typical aliphatic. group an alkylene group such as allyl oran'allsyl;

group, the methyl, ethyl, butyl, propyl, ,he cyl e c; a a om ic, one can usean aryl S abst tue t, but the ch an stand st c mmon s the nh nyl ro p. G n rally. the mcre ar cn atoms included in the compound, the greater is the Q91? lecting power. In the above formula, the sub.- stitution for hydrogen can bemade ,with' any number of substituents, that is, one, two, three or four, and the substituents can be different the several positions, that is, th compound can include "the "same group in two or more positions f as diphenyl urea; or two or more difierent grcups as ethyl 'phenyl urea and ethyl diphenyl urea.'

-'=1he-value-and'.practice of the invention wlll become durthen-apparent after consideration of the" following specific examples which are set-'iorth byway of illustration. rue test material cmployed was atypical sample of the-mill deed at Th sec pcynes are hl l i towards a single metal radical and'w-hen used I Frother 2 r the Bunker Hill & Sullivan: Mining- '8; Concentrating Co at Kellogg, Idaho,-and"compos ed"of one third-mine ore and'two thirds old jig tailings.-

The zinc sulphide in'the Bunker Hill 8: Sullivan ores-occurs as several varieties of" sphalerite, e. g.; a light-colored sph'a lerite which is very difllcult. to depress, followed 'by darker shades and ablack zinc sulphide; said to be marmatite a ferriferrcus variety containing 10% ormore of iron. High zinc losses are frequently attributedto the presence of marmatite'and thedifliculty floating it; The ore is inherentlydiflicult to treat forzi'ric and; consequently't-l' e rcoveryof 'z-inc in the zinc concentrate is w; The present standard practice on this ore includes g'rindingfof the feed to a fineness oi 62 minus 200 mesh and the addi tiqn Of the following 'reagntsto the ball millz QLWQ-i 99 ton of ore The frother mnployed was a mixture of 5% amyl alcohoLj-loit-"pine on and -Barretts No. 4gcoal tar creosotaflihe pI;I of the lead section was 7:1 and that of the zinc section {2. Reagents added to zinc "section:

m y Gcpper sulphate t s m can a Lead Zinc Lead; .Zinc.

Percent Percent Percent Percent 4.83 1135 100" 70. Q9 ,5. 01 91. 73 23. 48 3.23 53.14 94 55.38 ass 0.131U 7.33 21.14

In the tests conducted to illustrate this 'invention and reported-here asExamples i, 2-and"3,

the feed sample utilized contained 452% lead.

and 1.08% zinc. The feed sample was ground wet in a steel rod mill to 62% minus 200 mesh, the flotation reagents for the lead flotation being added to the rod mill. The pulp was then transferred to a GECO flotation cell which utilizes a combination of mechanical and pneumatic agitation. The oil mixture frother given above was used, but no other flotation reagent or depressing agent was employed. The pulp was subjected to agitation and aeration and the lead froth concentrate removed. The reagents for zinc flotation were then added to the flotation cell and the pulp again subjected to agitation and aeration and the zinc froth concentrate removed. Comparisons were made between the various flotation reagents contemplated by this invention with potassium ethyl xanthate following the previously described mill practice'on this ore feed. The results, shown graphically in Figures 1-, 2 and 3, are entirely from rougher concentrates with no cleaning steps.

Referring to the drawings, Figure 1 illustrates graphically the lead recovery with 0.1 lb. of urea per ton of ore while the amount of sodium carbonate was varied from 0.3 lb. per ton to 4 lb. per ton; also shown is the percentage of the total zinc which floated with the lead concentrate, as is the grade of the lead concentrate, i. e., the percentage of lead in the lead concentrate.

In Figure 2 are shown graphically the results obtained on this ore when the quantity of urea was varied from 0.03 lb. per ton to 0.4 1b., the sodium carbonate being held at a constant quantity of two pounds per ton, the per cent of the total zinc floating with the lead concentrate, and the grade of the lead concentrate.

In Figure 3 are shown graphically the results when the quantity of urea was varied and the sodium carbonate was held constant at 3 lb. per ton.

A study of these graphical "showings will reveal that the-lead recovery rises rapidly until 2 pounds of sodium carbonate is reached, a pH of approximately 8.0 for this ore. As the amount of sodium carbonate is increased beyond 2 pounds per ton, the lead recovery rises very slowly.

In the Bunker Hill & Sullivan ore, the leadz.inc ratio is high, about 4.5 to 1, while the zinc content in the feed is lower than in most lead zinc mill tails. -If more zinc is depressed by using depressing agents such as zinc sulphate or cyanide the recovery of lead is lowered. The total economic recovery of both lead and zinc determines the lead recovery and the corresponding percentage of the zinc in the lead concentrate.

"Z=3-potassium ethyl xanthate, fed with 0.15lb. pe'rton of sodium cyanideand 0.40 lb. of zinc sulfate. (Z is the registered trade-mark of The Dow Chemical Company for its xanthate flotation reagents.)

l A study of the results shown in Figures 1, 2 and 3 with the comparative results in Table 1 above show that the same results can be obtained with urea alone as with potassium ethyl xanthate and zinc sulphate and sodium cyanide as depressing agents.

- nomic recovery determined.

Urea has the advantage of being only approximately one-third the cost per pound of potassium ethyl xanthate; further, it does not require depressing agents to secure the same results, giving definite savings in reagent cost. It is a simple problem to control the amount of urea and the amount of sodium carbonate fed as these can be added automatically; it has been demonstrated that automatic feed of flotation reagents give improved operating results as compared to depending upon the operators judgment as to the amounts to be fed.

EXAMPLE II In Table 2 below, I have shown the results on this same ore with urea, the alkyl and aryl ureas, without the use of depressing agents, as well as the results with urea, the alkyl ureas, aryl ureas, and potassium ethyl xanthate using depressing agents for the zinc. Referring to Table 2, tests 4-9 show clearly the gradually increasing collecting power of the alkyl and aryl ureas as the number of carbon atoms increases; these also show the increase in the quantity of zinc which floats with the lead in this ore when no depressing agent is used.

Table 2 See notes below.)

L d Percerlit (gringo 'sodium ea Foulea percent ZlIlC lIl concen- Test Collector cagbgn meow lead mite,

ery concenpercent trate lead 0.1 2.0 92. 8 55. 1 53. 4 2. 3.0 92.6 54. 7 53. 6 0 21b 2.0 91. 7 47.1 56.0 4 0.2 lb. monoethyl urea. 2. 0 89. 9 50. 1 58. 6 5 0.1 lb. S-Di-n-butylurca... 1.0' 93. 1 G7. 3 59. 2 3.0 96. 5 73. 0 47. 9 3.0 96.1 67.1 51. 6 4.0 95.6 50. 4 52.0 3.0 94. 5 67. 2 54. 8 l. 1 92.9 56. 4 54. 7 4. 0 93. 3 54. 3 53. 7 2. 0 90. 4 35. 0 57. 8 2.0 91. 4 51. 7 56. 4 2.0 88. 9 49. 8 57.3 2.0 91. 8 58. 4 57. 5 87. 6 41. 5 60. 4 3.0 93. 3 64. 3 57.3 93. 3 64. 3 57. 3

10 and ll'fed with 0.15 lb. per ton of sodium cyanide and 0.4 lb. per ton of zinc sulfate.

12' and l7'fed with 0.8 lb. per ton of zinc sulfate.

l3*fed with 0.4 lb. per ton of zinc sulfate.

l4fed with 0.1 lb. per ton of sodium sulfate.

15*icd with 0.3 lb. per ttn of sodium cyanide.

l6 and 1S'fcd with 1.0 lb. per ton of sodium hydroxide.

The standard comparison test for potassium ethyl xanthate using depressing agents is given in Test 10. Tests 11-18 above show results when depressing agents are used with urea, the alkyl and aryl areas; while depressing agents may be used in conjunction with urea, alkyl ureas and aryl ureas, they are not essential.

A study of Table 2 will also bring out clearly the advantages of urea and its derivatives as collectors for lead. The results show an increase in collecting power affects both the lead: and zinc in the absence of a zinc depressant. If a zinc depressant is employed to suppress the zinc while floating the lead; some lead recovery is sacrificed to achieve any substantial depression of the zinc as compared to urea alone. While these results apply specifically to theBunker Hill and Sullivan ore treated, the selection and choice of reagents on an ore is determinedby thebest economic recovery rather than the best metallurgical recovery; the results in this table show the wide field of choice possible with urea and its derivatives.

EXAMPLE III Zinc sulphide requires a powerful collector and activation with copper sulphate for. successful flotation by either potassium ethyl .Xanthate or urea or its derivatives. forth the results on the test ore using, 0.33 lb.. per ton of copper sulfate to establish a comparison between potassium ethyl Xanthate following standard mill practice for the Bunker Hill 85 Sullivan ore and the derivatives of urea. It is to be noted that the use of S-Di-n-butylurea cut the loss of zinc in the tails approximately in half and at the same timedoubled approximately the grade of the concentrate.

Table 3 liirrxne, Percent Pfezcrruilt Gilda .s. ZlDC o o .a of Zlnq Tait 0011mm: per in zinc loss conto !v tails I .in tails centrate 1 10.0611). 7 3 f ;3 0.2 17.5 13.7 2-... 0.11b. phenyl urea 1.5 0.18 15.9 19.1 3.- 0.1 lb. diphenyl urea 1. 5 0.15 12. 5 20. 6 4.. 0.1 lb. buramine (70% 1.0 0.12 10.8 9. 8

n-butyl urea-% urea). 5..-. 0.1 lb. S-Di-n-butylurea 1.0 0. 10 8. 7 17. 1 6.--- do 2.0 0.10 8.9 25.2 7.--- d0 3. 0 0. 13 11. 2 24. 6

When depressing agents are used in the lead section for suppressing the flotation of the zinc with the lead concentrate, it is necessary to increase the lime to at least three pounds per ton, corresponding to a pH of approximately 9.2. The preceding lead float may employ potassium ethyl xanthate as a collector as well as urea and its derivatives without affecting the zinc float except when used in conjunction with depressing agents mentioned before. The black sphalerite is seen in the tails under a microscope when the tails are high. They are absent when the tails are low. When the tails are low, the concentrate assumes a salt and pepper appearance to the naked eye and, under the microscope, the black sphalerite can be clearly identified. It is probable the superior recovery is due to an improved collecting power for the more difficult varieties of sphalerite in this ore.

The pH on the Bunker Hill & Sullivan ore for the corresponding amounts of lime is given below:

The concentrate grade is higher with the higher pH and, as the urea derivatives give better results with a higher lime, the depression of the pyrite is better. It will be noted in Table 3 In Table 3 I have set 6. that the standard .mill practice requires 0.3 1119; lime with a. pH of 7.2, which is not favor-ableo for depressing Pyrite.

The several examples given above show the general characteristics of urea and its. derivatives. as collectors for. lead and .zincrminerals. Tests with pure minerals showyureahasvery little-selective action towards pyrite; Due: to the good. collecting action of the; urea derivatives: with a .high. pH. and withxlime, good. depression Of pyrite is secured, andpyrite plainlytidentifiable under the microscope when the zinc concentrate grade is high, as is shown by Example III.

Urea is water soluble as are methyl, ethyl, butyl and diethyl urea; dibutyl urea, phenyl and diphenyl ureas are only slightly soluble in water, but all are solublein methyl alcohol and can be fed'in. solution, Those which are insoluble or, only slightly soluble are miscible with. water and can, be fed dry to the rod mill preceding he lead. float and with the copper sulphatepreceding the zinc float.

Urea is used in large; quantities for a ,numberof purposes in the chemical industry and is readily procurable from a number of chemical manufactu-rers, As a colleeton; itspric'eis aboutya third approximately of other collectors on the market. The commercial manufacture ofthe alkyl and aryl m'eas has", in most cases, been worked out, and several areonv themarket The characteristics are shown so that any one versed in the flotation art may in the usual manner by tests apply urea and its derivatives to a leadzinc ore flotation problem.

I claim:

1. A method of. differential froth flotation which comprises subjecting an aqueous alkaline pulp of an ore containing lead and zinc to froth flotation in the presence of a frother and in the presence of a reagent included in the group having the following formula:

where R1 and R3 are hydrogen atoms and R2 and R4 are members chosen from the group including hydrogen, aliphatic radicals and aromatic radicals, and removing therefrom a concentrate containing lead and a tailing rich in zinc.

2. A method of differential froth flotation which comprises subjecting an aqueous alkaline pulp of an ore containing lead and zinc to froth flotation in the presence of a frother and in the presence of a reagent included in the group having the following formula:

where R1 and R3 are hydrogen atoms and R2 and R4 are members chosen from the group including hydrogen, aliphatic radicals and aromatic radicals, removing therefrom a concentrate containing lead and a tailing rich in zinc, activating the zinc with copper sulfate subjecting an aqueous alkaline pulp of the tailing to froth flotation in the presence of a reagent included in the group having the following formula:

where R1 and R3 are hydrogen atoms and R2 and R4 are members chosen from the group including hydrogen, aliphatic radicals and aromatic radicals, said pulp having a pH between 8.0 and 9.0 and being free of any depressing agent for pyrite and sphalerite present in the ore, and removing therefrom a concentrate containing lead and a tailing rich in zinc.

4. A method of differential froth flotation which comprises subjecting an aqueous alkaline pulp of an ore containing lead and zinc to froth flotation in the presence of a frother including coal tar creosote in the presence of a reagent included in the group having the following formula:

where R1 and R: are hydrogen atoms and R2 and R4 are members chosen from the group including hydrogen, aliphatic radicals and aromatic radicals, said pulp having a pH between 8.0 and 9.0 and being free of any depressing agent for pyrite and sphalerite present in the ore, and removing therefrom a concentrate containing lead. a tailing rich in zinc, activating the zinc with copper sulfate subjecting an aqueous alkaline pulp of the tailing to froth flotation in the presence of a reagent included in the group having the following formula:

R: Re

where R1 and R3 are hydrogen atoms and R: and R4 are members chosen from the group including hydrogen, aliphatic radicals and aromatic radicals, said pulp having a pH between 8.0 and 9.0 and being free of any depressing agent for pyrite and sphalerite present in the ore, and removing therefrom a zinc concentrate.

PIERRE R. HINES.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,208,171 Lavers Dec. 12, 1916 1,301,551 Freeman Apr. 22, 1919 1,448,929 Luckenbach Mar. 30, 1923 OTHER REFERENCES :Transactions of the American Institute of Mining and Metallurgical Engineers, 1930, pages 301-302. (Copy in Div. 25.)

Taggart, Handbook of Mineral Dressing, (c) 1945, section 12, page 113. (Copy in Div. 25.) 

1. A METHOD OF DIFFERENTIAL FROTH FLOTATION WHICH COMPRISES SUBJECTING AN AQUEOUS ALKALINE PULP OF AN ORE CONTAINING LEAD AND ZINC TO FROT FLOTATION IN THE PRESENCE OF A FROTHER AN IN THE 